1. Field of the Invention
The present invention generally relates to the art of packaging and, more particularly to a bagging and packaging machine for successively forming bags from a strip of bag material and subsequently packaging an article into each of the bags.
2. Description of the Prior Art
In general, the bagging and packaging machine for successively forming bags from a strip of bag material and subsequently packaging an article into each of the bags undergoes a process of forming the strip of bag material, supplied to a bag former, into a tubular form by means of the bag former by overlapping opposite longitudinal side edges with each other; fusion bonding, by means of a longitudinal sealing unit, the overlapped longitudinal side edges of the tubular strip of bag material in a direction longitudinally thereof at an outer surface of a front wall of an article introducing tube member forming a part of the bag former and, concurrently, fusion bonding the tubular strip of bag material in a direction perpendicular to the longitudinal sense of the tubular strip of bag material to form a bottom seal by means of a transverse sealing unit. After an article has been introduced into the tubular strip of bag material through the article introducing tube member, the machine carries out fusion bonding an upper portion of the tubular strip of bag material by means of the transverse sealing unit to form an upper seal to seal the article within the tubular strip of bag material; and finally cutting the tubular strip of bag material along the upper seal to thereby to produce a bagged product containing the article sealed within the bag.
In the practice of this process, where the article filled in each of the successively formed bags is food material, it is a general practice to form the upper seal in the bag after an inert gas such as, for example, nitrogen gas or argon gas has been substituted for air within the bag containing the article therein. The Japanese Laid-open Patent Publication No. 10-53217, for example, discloses,the technique necessitated for this purpose.
The gas replacement device disclosed in the above mentioned publication includes, as shown in FIG. 8, a substitute gas supply passage B extending in a vertical direction along an inner surface of the article introducing tube member A, which passage B has a gas inlet B1 defined at an upper end thereof and a gas outlet B2 defined at a lower end thereof. An inert gas to be substituted for the air within the bag is supplied into the substitute gas supply passage B through the gas inlet B1 and is discharged through the gas outlet B2 into the bag-shaped packaging material C. The inert gas thus supplied into the bag-shaped packaging material C expels the air therefrom so that the inert gas can substitute for the air.
On the other hand, in recent years, the handling capacity of the packaging machine has been desired to increase further. If the rate of replacement with the inert gas is desired to be maintained at a high level in an attempt to increase the handling speed, the flow rate or velocity of the inert gas has to be increased so that the amount of the inert gas supplied per unitary time can be increased. However, increase of the gas flow velocity tends to result in that as shown in FIG. 8, the inert gas is vigorously introduced from the gas outlet B2 at the lower end of the substitute gas supply passage B into the bag-shaped packaging material C and, consequently, some of items X, X, . . . X of the article to be bagged are blown upwardly within the bag-shaped packaging material C or a sufficient introduction of the items X, X, . . . X of the article towards the bottom of the bag-shaped packaging material C is hampered. In such case, when the upper seal is to be formed in the filled bag-shaped packaging material C by means of the transverse sealers D and D of the transverse sealing unit, some of the items X, X, . . . X of the article which have been blown upwards within the bag-shaped packaging material C or which have been retarded to reach the bottom of the bag-shaped packaging-material C are often xe2x80x9cbittenxe2x80x9d by the transverse sealers D and D, resulting in a defective bagged product.
In an attempt to obviate problems brought about by the blow-up within the bag-shaped packaging material C, it may be contemplated to increase the cross-sectional area of the substitute gas supply passage B over the entire length thereof. However, increase of the cross-sectional area of the substitute gas supply passage B necessitates reduction of the cross-sectional area of the tube member A, which in turn results in lowering the speed at which the items X, X, . . . X of the article are introduced into the bag-shaped packaging material C through the tube member A or clogging of some of the items X, X, . . . X of the article within the tube member A. The consequence is that introduction of a required or desired quantity of the items X, X, . . . X of the article into the bag-shaped packaging material C through the tube member A will take a relatively long time, hampering a high speed packaging operation, or otherwise a possibility will arise that some of the bagged products may contain an insufficient quantity of the items X, X, . . . X of the article.
Also with the prior art structure disclosed in the previously discussed publication, since as shown in FIG. 8 the gas outlet B2 at the lower end of the substitute gas supply passage B opens inwardly of the tube member A, an air curtain of the inert gas discharged from the substitute gas supply passage B is formed at a lower end region of the tube member A, hampering a smooth introduction of the article into the bag-shaped packaging material C through the tube member A. As a result, the handling speed during the packaging operation tends to be lowered, or a possibility will arise that some of the bagged products may contain insufficient quantity of the items X, X, . . . X of the article.
Accordingly, the present invention has been devised to provide an improved bagging and packaging machine of a type having a gas flush capability, in which the inert gas can be sufficiently introduced to achieve a high rate of gas replacement with neither possibility of the article being bitten, or possibility of the packaging speed being lowered during the sealing of the filled bag.
In order to obviate the problems discussed above, the present invention is featured in that the bagging and packaging machine is constructed as follows.
In the first place, the present invention provides a bagging and packaging machine which includes al bag former including a sailor member and a tube member connected with the sailor member and operable to form a strip of packaging material into a tubular form with opposite longitudinal side edges thereof overlapping with each other, a vertical sealing means for sealing the overlapping longitudinal side edges of the strip of packaging material, which has been formed into the tubular form by the bag former, to provide a longitudinally sealed tubular packaging material, a transverse sealing means for sealing the longitudinally sealed tubular packaging material in a direction generally perpendicular to a longitudinal sense of the longitudinally sealed tubular packaging material to render the latter in a bag form, with articles being introduced into the bag-shaped longitudinally sealed tubular packaging material through the tube member. The bagging and packaging machine further includes a substitute gas supply passage provided inside the tube member for introducing a substitute gas into the bag-shaped longitudinally sealed tubular packaging material for replacement with air inside the bag-shaped longitudinally sealed tubular packaging material. The substitute gas supply passage has a cross-sectional area that is greater at a downstream side thereof than at an upstream side thereof with respect to a direction of flow of the substitute gas.
Preferably, the substitute gas supply passage has a cross-sectional shape having a width that is large at the downstream side thereof such that the substitute gas supply passage has a cross-sectional area that is larger at the downstream side thereof than at the upstream side thereof.
Alternatively or in combination therewith, the substitute gas supply passage preferably has a cross-sectional shape having a thickness that is large at the downstream side thereof such that the substitute gas supply passage has a cross-sectional area that is larger at the downstream side thereof than at the upstream side thereof.
Also preferably, the substitute gas supply passage has a downstream end at the downstream side thereof that is left open in a direction outwardly of the tube member.
In addition, a longitudinal portion of the tube member, which confronts a wall having a surface where the opposite longitudinal side edges of the strip of packaging material are overlapped, is preferably left open.
According to the present invention, since the substitute gas supply passage provided in the tube member forming a part of the bag former has a cross-sectional area that is larger at the downstream side thereof than at the upstream side thereof, it is possible to supply a required quantity of the substitute gas into the bag-shaped longitudinally sealed tubular packaging material at a relatively moderate flow velocity through the opening at the lower end thereof without the cross-sectional area of the article introducing passage within the tube member being unnecessarily narrowed such as occurring in the case where the substitute gas supply passage has a large cross-sectional area over the entire length thereof from the upstream side down to the downstream side thereof Accordingly, without the efficiency of the packaging operation being lowered, and also without the rate of replacement of the gas being lowered, the inconvenience hitherto experienced with the biting of some of the articles which occur when some of the articles within the bag-shaped longitudinally sealed tubular packaging material are blown up by the flow of the substitute gas can advantageously be avoided, thereby avoiding production of defective bagged products.
According to a preferred embodiment of the present invention, since the substitute gas supply passage has a cross-sectional shape having a width that is large at the downstream side thereof and/or having a thickness that is large at the downstream side thereof, the cross-sectional area of the substitute gas supply passage can easily be set larger at the downstream side thereof than at the upstream side thereof.
Also, according to a preferred embodiment of the present invention, since the end of the substitute gas supply passage at the downstream side thereof is left open outwardly of the tube member, there is no possibility that an air curtain of the substitute gas emerging from that opening will be formed at the gas outlet of the tube member, thereby eliminating the possibility that introduction of the articles into the bag-shaped longitudinally sealed tubular packaging material will be hampered.
Again, according to a preferred embodiment of the present invention, since the longitudinal portion of the tube member, which confronts a wall having a surface where the opposite longitudinal side edges of the strip of packaging material are overlapped, is left open, any clogging of the articles to be bagged is advantageously avoided and thus, the introduction of the articles to be bagged through the tube member can take place smoothly in view of the additional fact that the cross-sectional area of the upstream portion of the substitute gas supply passage is so narrowed to secure a sufficient cross-sectional area of the tube member for the introduction of the articles therethrough. Accordingly, any possible reduction of the handling speed can advantageously be further avoided.